Sodium peroxide manufacture



March 1954 L. J. GOVERNALE 2,671,010

SODIUM PEROXIDE MANUFACTURE Filed Nov. 29. 1951 INVENTOR. LUKE J.GOVER/VALE' Patented Mar. 2, 1954 q UNITED STATES PATENT orn-cc IS'DDIUMIQERBXIDE MANUFACTURE Luke J, .Governale, Baton Rouge, La., assignor toEthyl Corporation, vNewYork, N. 1 a corp oration 'of Delaware.AplilicationzNovcmher 29, 19.51,-Ser.ialNo. 258;!)33

'i'fllaims. (Cl.'2 3184) ;1 The present invention relatesto theproduction of sodium peroxide, more particularly its formation frommetallic sodium.

Sod-ium peroxide has heretofore been .made

by several different methods. .See for example I U. S. Patent Nos.1,796,241 and 1,685,520. Such :methods have disadvantages in that theyinvolve a two step procedure requiring :separate treat ment stepsperformed in difierent manners. .Such prior techniques require, forexample, the stepwise and :batchwise processing of large charges,necessitating large and cumbersome equipment. Further, an oxidizingatmosphere having an oxygen content higher than that prosent-in' is rquired. The oxidation ofsodium by a spray burning method has beenproposed, but the product so obtained .is not entirely satiso :factoryfor many purposes, being somewhat too light and flulfy for easy handlingand dissolving.

Among the objects of the -,present*inventionvis the provision of novelmethods and apparatus for producing sodium peroxide in which the aboveand related disadvantages are avoided- Additional o j s of the presentinvention in- %clude the provision oi novel. methodsiandiappav.ratus foroxidizing sodium to sodium peroxide wi hout equiring the treatment ofiarge masses or sodium, and without producing explosive rmixtures orfumes. A still zfurther object of the present invention is the provisionof novel methiods and apparatus :for rapidly oxidizing sodium :to sodiumperoxide essentially :in runenriched .a'ir. An additional object is "toprovide an eflicient continuous process for the manufacture of commerc'ially acceptable sodium peroxide.

The above as well as still further objects of the present invention-willbe more completely understood from the following description :of:several of its exemplifications, reference :being made to theaccompanying drawing wherein the :single :fi ure shows in schematic form:a sodium :peroxide forming apparatus in accordance with the presentinvention.

It has been discovered that very efiective oxidation of sodium directlyto :sodium iperoxidecan be readily attained by providing :a ithin filmof sodium deposited on a carrierrsurface, and contacting this film withan oxidizing atmosphere at an elevated reaction temperature until it is-substantially converted to sodium peroxide, then parting from thesupporting metal surface as a :comminuted product. Inpref'erred formsolthe process, the oxidizing gas, which may he air or an enriched oxygenstream, "is forcibly directed against the sodium filmas a gaseou ,jet ora V .2 multiplicity of ,jets. Thus, for example, a one millimeter .filmof sodium is converted to a predominantly sodium peroxide product inabout '15 minutes. Atihig'her temperatures'the .rate of conversion iseven higher. The product. obtained is in a .des'irable form, being inrelatively homogeneous or dense particles, as contrasted with the lightand .flufiy material derived 'by other continuous .methods.

The process is operable at'quite moderate temperatures, that is, attemperatures in the range of about 300 C. Although the benefits of theprocess are obtained to .an extent at such relatively moderatetemperatures, the outstanding .benefit of a rapid reaction is greatlyreduced. .1 13 has been found that the oxidation of the sodium in themanner described, when expressed in terms of conversion .to sodiumperoxide at \dif feren't times, but at .a controlled temperature,apparently usually exhibits a ,period of rapid or primary reaction, andthen-a period of relatively slow or secondary reaction. Thus, incarrying out the oxidation of a one millimeter film at about 360 theinitial period appears to last .for about five minutes, and thereaiteradditio al oxidation isso slow that approximately one hour is requiredto provide a product of 8 0 percent or more sodium peroxide .=oontent.When operating at 400 0., the initial period is slightly longer, orabout seven minutes, and the subsequent secondary oxidation at a lowerrate. When operatingatabout 450 Ccor higher, the socal ed secondaryreaction period appears to disappear, or to :merge with the primaryperiod, As a result, in the relatively brief period of about 15 minutesat 450 0., the reaction is complete, with no additional oxidation occur-.ring. .A product having approximately 90 percent sodium peroxide isproduced.

At temperatures above 450 -C., the time re .quired .for oxidation isdecreased still further, .50 thatthe capacity of a given plant :isincreased. Satisfactory conversion is attained at temperatures of theorder .of 6.00 C., but. for several reasons, the upper limit of thepreferredoperating temperature range is about 575 C. -It has been foundthat above this temperature, the sodium peroxide tends to decompose morestrongly than at lower temperatures, and that, therefore, it .isappreciably more dir'licult to ob? tain a product of acceptable purity.Further, the corrosive tendency ofsodiumperoxidegrea ly in-cr ase attemperatu es approaching 600 C which tends to limit the life of theequipment.

afiected to some extent by the thickness of the film of sodium beingprocessed. Films thicker than one millimeter can also be used throughoutthe entire range at the cost of some increase in conversion time.However, when the sodium is deposited at a rate thicker than a onemillimeter film, the overall degree of conversion is slightly reduced.The adverse effect of thickness is partially offset by the effect of thejets of air, which appear to penetrate through the initially oxidizedsurface to the full depth of the film. On the other hand, films thinnerthan one millimeter are rapidly converted. However, the effect ofreduction of thickness below one millimeter is not as marked as theefi'ect of reducing the film thickness to one millimeter.

For practical operations it is advantageous that the process of thepresent invention be carried out in a continuous manner. By providing acarrier having an extended surface occupying an endless or looped path,and arranging for this surface to be continuously recycled around saidpath, the sodium can be continually applied at one portion of the path,followed by exposure of the sodium to air and the subsequent continualremoval of the final oxidized product at a different portion of the pathafter which the surface is ready for another application.

The figure shows a convenient modification of an apparatus according tothe present invention. A housing l carries within it a cylindrical druml2 mounted for rotation around its cylindrical axis in the direction ofthe arrow l4. Above the drum there is positioned an applicator ordistributor H; which may merely be in the form of anelongated pipehaving a plurality of outlet nozzles I8 distributed along its lengths soas to extend across the axial length of drum l2. The applicator i fed bya source of molten sodium, shown as a container 20 which may be withinor outside of the housing 10.

To avoid difficulties that may arise if the sodium solidifies inapplicator l6, or container 2|), these structures may be provided withan external heating jacket through which hot liquid, such as oil, may bepassed to heat them up or keep them from cooling suificiently to causesolidification. Such jacketing is conventional and in the interest ofsimplicity is not shown in the drawing.

The drum I2 is arranged to be held at the desired operating temperature,as by placing its interior in communication with an oil burner. This canbe conveniently done by merely mounting an oil burner at one end of thecylinder and connecting a chimney or other vent to the other end.Although heat is liberated during the oxidation of the sodium, this heatis not sufiicient to keep the reaction mixture at temperatures as highas 450 C. for example.

Along the cylindrical periphery of drum 12 there is shown mounted aplurality of air nozzles 2|, 22, 23, 24 and 25, each connected to asuitable source of air such as a small blower, and each positioned todirect a stream of air against the external surface of drum 12 as thissurface moves past applicator l6 and picks up sodium. It is advisable touse only dry air in the air nozzles, and for this purpose they can beconnected to a source of fresh air by way of a drying unit to absorbsubstantially all moisture.

A scraper blade 30 is shown as engaging the external surface of drum [2beyond the air nozzles to scrape off the reaction product 32, whichproduct remains on the drum surface. A collecting trough 34 canconveniently be positioned below the scraper blade 30 to catch theremoved product and if desired, automatically carry it out of thehousing 10 continuously or in separate batches.

The apparatus can be operated by heating up the drum, introducing airthrough the air nozzles, and then starting th application of sodium. Thesodium begins to oxidize as soon as it is exposed to the oxidizingatmosphere, but this factor, far from being disadvantageous, assists inretaining the film on the drum surface. This surface oxide film, beingsolid at operating temperatures, tends to prevent flow of the metallicsodium off of the drum and facilitates application. It is preferred toadjust the feed rate of the sodium by valve I! to provide a film ofabout one millimeter thickness or less. Inasmuch as the drum 12 can bearranged for operation at a substantially constant speed, the rate ofapplication can also be fixed.

The housing In can be arranged to completely seal in the above units,except for a vent for the escape of xcess or reacted air. Since thisexcess gas, lean in oxygen content is very dry, it can be used in otherapplications where a dry atmosphere is needed. The escaping gas can alsobe filtered to catch particles of sodium or its oxidation products whichmay be picked up during passage through the housing In. By reason of therelatively high temperatures to which the escaping air is heated by thpreferred type of operation, it can also be used to supply heat wheredesired.

Instead of having a cylindrical drum as shown in the figure, thesodium-carrying surface can be in the form of a flexible sheet metalbelt which can be looped around one or more rollers to provide acorresponding cyclical travel around an endless path. In such amodification heating can be applied by way of the roller or rollersaround which the band is looped, or the air blown against the metalsurface can be preheated.

Alternatively the endlessly recycling sodiumcarrying member can be inthe form of a fiat surface, such as that of a circular disc, androtating around its center with sodium applied at one part of therotation, the air exposure at a second part, followed by a scraper bladeat a third part. This type of structure has th advantage of makingpossible the spreading of the reaction over substantially the entirerecycling path of the sodium-carrying surface. This will be evident bynoting that in the drum construction illustrated in the figure, aboutone-third of the drum periphery is not used for oxidation. The disc typeof sodium holder can conveniently be heated by making the disc hollowand introducing heat to the hollow interior as in the manner describedabove in connection with the drum of the figure. If desired, heated aircan also be used to heat the reaction mixture held on the discshapedcarrier, or on the drum carrier of the figure.

Instead of blowing air into the housing, advantage can be taken of thenatural draft that can be provided by the exhausting hot air. Thus bymerely providing a sutiable chimney, the air blower can be eliminated.

As a further modification of the present invention, the number of airnozzles can be reduced or they can be completely eliminated and replacedby a single air inlet which can be simply provided at the wall ofhousing l0. Where one or more separate nozzles are used, one such nozzlecan also be positioned to direct a stream of air somewhat enrichedwithoxygen against the sodium-carrying surface at a point just before thefinal product is removed. This is particularly suitable when theoperation is carried out at temperatures below 450 C., inasmuch as afinal contact of the oxidizing materials with an atmosphere containingmore than 20 percent oxygen will greatly accelerate the completion ofthe oxidation, without requiring an excessive expense in the provisionof an oxidizing atmosphere. It is advantageous in this form of theinvention to provide an enclosing duct to keep the enriched air againstthe drum so that it does not dissipate too rapidly throughout thehousing. The useful volume of enriched air can thereby be held down tosubstantially insignificant proportions.

The precise location of the scraper or doctor blade 39 is not critical.However, on the drum type reactor of the figure, it should be verticallypositioned at or below the axis of the drum. This assures that theproduct as it is removed from the drum will fall clear and can becollected in a suitable receptacle or hopper 34. Location of the doctorblade in the region indicated will also provide the maximum practicalreaction time for a given size drum. With the disc type sodium carrier,no special scraper location is needed. It is not essential that thedoctor blade should scrape the drum surface entirely clear or free ofthe sodium peroxide product. In fact, it has been found desirable toallow a thin coating of the product to remain on the metal surface by aloose contact of the doctor blade. The effect of this recycled adherentcoating is to minimize the corrosion of the metal drum and to assure ahigh purity product, that is, free of contaminants resulting fromcorrosion reactions.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope hereof, it is to beunderstood that the invention is not limited to the specific embodimentshereof, except as defined in the appended claims.

What is claimed is:

1. A method of producing sodium peroxide which method is characterizedby pouring a film of liquid sodium not more than about one millimeterthick over the external surface of a rotatable carrier heated to betweenabout 450 and 575 C., rotating said carrier through a stream of airdirected against said heated film, the air being at a rate in excess ofthe quantity required for completely converting the sodium to sodiumperoxide, for not more than about fifteen minutes 55 till the film islargely converted to sodium peroxide, and scraping off the resultingproduct.

2. The method as defined in claim 1 in which the carrier is rotated insuccession through a plurality of streams of air.

3. A method of producing sodium peroxide comprising continuouslydepositing a thin film of sodium, having a thickness of not more thanabout one millimeter, on the exterior surface of an endless moving heattransmissive metal carrier, contacting a stream of air against said filmat a rate in excess of the quantity necessary for completely convertingthe sodium to sodium peroxide, while heating the carrier to atemperature between about 450 and 575 C., continuing said contacting fornot more than about 15 minutes until the sodium is largely converted tosodium eroxide, and then parting said peroxide from the said surface.

4. A method of producing sodium peroxide comprising depositing a film ofsodium having a thickness of not more than about one millimeter on theexterior surface of an endless moving heat transmissive metal carrier,directing a plurality of jets of air against said film for a conversiontime providing substantially complete conversion of the sodium to sodiumperoxide while heating the carrier in an initial portion of not morethan about 15 minutes of the conversion time to a temperature in therange of from above 450 to 575 C., and in the following portion to atemperature in the range of about 300 to 450 C., and parting theso-formed sodium peroxide from the said surface.

LUKE J. GOVERNALE.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Handbook of Chem. and Physics, 27th ed., 1943, pp. 462, 463.Published by Chem. Rubber Pub. 00., Cleveland, Ohio.

1. A METHOD OF PRODUCING SODIUM PEROXIDE WHICH METHODS IS CHARACTERIZEDBY POURING A FILM OF LIQUID SODIUM NOT MORE THAN ABOUT ONE MILLIMETERTHICK OVER THE EXTERNAL SURFACE OF A ROTATABLE CARRIER HEATED TO BETWEENABOUT 450* AND 575* C., ROTATING SAID CARRIER THROUGH A STREAM OF AIRDIRECTED AGAINST SAID HEATED FILM, THE AIR BEING AT A RATE IN EXCESS OFTHE QUANTITY REQUIRED FOR COMPLETELY CONVERTING THE SODIUM TO SODIUMPEROXIDE, FOR NOT MORE THAN ABOUT FIFTEEN MINUTES TILL THE FILM ISLARGELY CONVERTED TO SODIUM PEROXIDE, AND SCRAPING OFF THE RESULTINGPRODUCT.